This invention relates to a heavy duty suspension system, and more particularly, the invention relates to a trailing arm suspension system.
Various types of suspension configurations have been used for heavy duty applications. For drive axles, the suspension geometry affects a pinion angle. The pinion angle is the angle between an axle input shaft axis and a drive shaft axis. It is desirable to have as little pinion angle as possible to reduce wear. Additionally, it is desirable to have equal angles for the drive shaft axis and the axle input shaft axis and the transmission output shaft axis to balance the forces on the yokes.
Trailing arm suspensions have been employed for heavy duty applications, such as for motorhomes. An axle may be rigidly or pivotally secured to the trailing arm. For drive axle trailing arm suspensions, such as for motorhome applications, the pinion angle of the axle is frequently defined by an upper attachment member. The upper attachment member and the trailing arm define the pinion angle during the operation of the suspension. One suspension configuration has employed a rod arranged longitudinally between the frame and the axle to define the pinion angle. This configuration additionally employs a lateral rod connected between the axle and the frame. Such a configuration of rods has the undesirable effect of moving the axle input shaft along an arcuate path in a vertically lateral plane during suspension operation. Instead of the rods, the upper attachment member may be defined by a triangular plate. The apex of the plate is pivotally attached to the axle and the side opposing the apex is attached between opposing frame rails. However, the plate lacks sufficient structural integrity as an upper attachment member and is difficult to install and service.
Suspension systems utilize anti-roll bars to stabilize the vehicle during a turning maneuver. One conventional type of anti-roll bar utilized on passenger vehicles includes ends that are secured to a suspension component such as a lower control arm. A central portion extends between the ends and is supported on the frame of the vehicle by brackets and bushings. As the control arms move during a turning maneuver, the anti-roll bar rotationally deflects and acts against the frame to provide vehicle stability. Supporting an anti-roll bar by a frame for heavy duty vehicle applications is not practical since the suspension components may be spaced a significant distance from the frame so that a portion of the frame may not be located sufficiently close to the anti-roll bar.
A heavy-duty trailing arm suspension system has been proposed that utilizes a torque tube extending between the trailing arms. The torque tube is welded to an adaptor plate that is supported by numerous bushings. To service the torque tube, the adaptor plate and all of the supported suspension components must be removed. The adaptor plate supports many other suspension components such as a shock absorber and/or air spring. The adaptor plate may also support the axle. As a result, the numerous bushings receive load inputs from various components. Accordingly, it is difficult to isolate any one bushing to optimize the roll characteristics.